#include "crc_16.h"
#include "string.h"
#include "stdint.h"

static uint16_t ccitt_table[256] = {
0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
};

uint16_t crc_ccitt(uint8_t *q, uint16_t len)
{
  uint16_t crc = 0;
  while (len-- > 0)
  {
    crc = ccitt_table[(crc >> 8 ^ *q++) & 0xff] ^ (crc << 8);
  }
  return ~crc;
}

#define CRC_SEED  0xFFFF  // 该位称为预置值，使用人工算法（长除法）时需要将除数多项式先与该与职位异或，才能得到最后的除数多项式
#define POLY16 0x1021    // 该位为简式书写实际为0x11021
uint16_t crc16(uint8_t *buf,uint16_t length)
{
  uint16_t shift,data,val;
  uint32_t i;
  shift = CRC_SEED;

  for(i=0;i<length;i++) 
  {
    if((i % 8) == 0)
      data = (*buf++)<<8;
    val = shift ^ data;
    shift = shift<<1;
    data = data <<1;
    if(val&0x8000)
    shift = shift ^ POLY16;
  }
  return shift;
}


uint16_t GetCRC16( uint8_t* bufData, uint16_t sizeData )
{
	uint16_t CRC, i;
	uint8_t j;
	CRC = 0;
	for( i=0; i<sizeData; i++ )
	{
		CRC ^= bufData[i];
		for( j=0; j<8; j++ )
		{
			if( CRC & 0x001 )
			{
				CRC >>= 1;
				CRC ^= 0x08408;
			}
			else
			{
				CRC >>= 1;
			}
		}
	}

	return CRC;
}

/****************************************************************************
名称: UART_CRC16_Work()
说明: CRC16校验程序
参数: 		*CRC_Buf:数据地址
                       CRC_Leni:数据长度
返回:                   CRC_Sumx:校验值
*****************************************************************************/
uint16_t UART_CRC16_Work(uint8_t *CRC_Buf,uint8_t CRC_Leni)
{
	uint8_t i,j;
	uint16_t CRC_Sumx;

	CRC_Sumx=0xFFFF;
	for(i=0;i<CRC_Leni;i++)
	{
		CRC_Sumx^=*(CRC_Buf+i);//异或
		for(j=0;j<8;j++)
		{
			if(CRC_Sumx & 0x01)
			{
				CRC_Sumx>>=1;	
				CRC_Sumx^=0xA001;
			}
			else
			{
				CRC_Sumx>>=1;
			}
		}	
	}
	return (CRC_Sumx);
}




